Combustible fuel igniting apparatus

ABSTRACT

Fuel ignitor apparatus especially adapted for use in a commercial baking oven having a plurality of fuel burner tubes susceptible of movement in response to changes in ambient temperature. The ignitor apparatus associated with each burner tube is coupled to the latter for movements therewith. Each ignitor is mounted on a wall of the oven in such manner as to enable bodily movement of such ignitor relative to the oven so as to avoid imposing bending stresses on the ignitor or the oven.

This invention relates to apparatus especially adapted for use in anoven of a commercial bakery for igniting a combustible fuel issuing froma burner and maintaining the ignitor in a predetermined positionrelative to the burner.

BACKGROUND OF THE INVENTION

In a conventional commercial bakery a gas fired oven defines anenclosure or combustion chamber through which goods to be baked areconveyed longitudinally of the oven by chain or other conveyors.Extending transversely of the path traversed by the conveyors is aplurality of burner tubes which are spaced apart from one another so asto enable the interior of the oven to be heated to desired temperaturelevels.

Each burner is coupled to a source of combustible fuel, such as naturalor propane gas, and each burner is provided with ribbon or other fueloutlets through which the gas may pass for combustion. At a selectedpoint along the length of each burner is positioned a fuel ignitor bymeans of which fuel flowing through the burner outlet may be ignited.

The temperature in the oven normally is controlled by varying the numberof burners which are lighted at any given time. For higher temperatures,as may be required by the proper baking of some goods, all or most ofthe burners are ignited. In other instances, in which the goods beingbaked do not require higher temperatures, some of the burners may beidle or turned off.

It is conventional to provide as part of the fuel igniting apparatus aspark generator and a flame sensor which is operable to sense thepresence or absence of flame issuing from a burner. When fuel initiallyis discharged from a burner tube it is conventional to ignite such fuelby means of the generation of sparks and form a flame. If the presenceof the flame is sensed, the ignitor is disabled. If no flame is sensedafter a predetermined time, the ignitor and the flow of fuel through theaffected burner are terminated.

The temperature within the oven affects the materials, usually metals,from which the burner tube and the ignitor apparatus are made. Ingeneral, the burner and ignitor apparatus materials expand when heated,and contract when cooled. However, due to the differences in materialsand differences in lengths of such apparatus, the expansion andcontraction rates are not the same, thereby resulting in distortion andmovements of the burner and ignitor. Accordingly, it is preferred toattach the ignitor apparatus to the burner tube so that the ignitorapparatus will move in accordance with the movements of the burner tubewhich, in some instances, may be as much as several inches orcentimeters.

Both the burner tubes and the ignitor apparatus associated with eachtube extend into the oven from the exterior thereof. Both the burnertubes and the associated ignitor apparatus conventionally are supportedon a wall of the oven. In those instances in which a burner tube moves asignificant distance due to thermal changes, the associated ignitorapparatus may have to move a significant distance also since it isconnected to its associated burner tube. Repeated movements of theignitor apparatus in response to movements of its associated burner tubeimposes significant stress on the component parts of the ignitorapparatus which, in time, can result in structural failure of suchapparatus.

Fuel ignitor apparatus that has functioned very well following itsintroduction to the industry is disclosed in Glidden U.S. Pat. No.6,808,389. Ignitor apparatus constructed in accordance with the presentinvention incorporates many of the advantageous characteristics of thepatented apparatus, but includes improvements which enhance itsoperation and minimize its expense.

SUMMARY OF THE INVENTION

Ignitor apparatus constructed in accordance with a preferred embodimentof the invention comprises an electrically conductive outer supportsleeve through which extends an electrically conductive ignitorelectrode, the electrode being electrically insulated from the outersleeve by insulators. An electrically conductive, flag-like fuelconcentrator is fixed at one end of the outer sleeve and is sopositioned adjacent the ignitor electrode as to establish a gap ofpredetermined width therebetween which may be traversed by sparks forthe purpose of igniting fuel issuing from the burner tube. That end ofthe ignitor sleeve adjacent the fuel concentrator is fastened to theadjacent burner tube so as to move with the latter as it flexes inresponse to temperature variations. The opposite end of the ignitorsleeve extends through an opening in the oven wall and is accommodatedin a bushing in such manner as to be rockable about a vertical axis. Thearrangement is such that, when the burner tube deflects, the ignitorwill move accordingly, but instead of bending, the sleeve will rockabout the vertical axis, thereby avoiding the imposition of bendingstresses on the ignitor apparatus.

The construction of the ignitor apparatus disclosed herein enables theadvantageous characteristics of the apparatus shown in theaforementioned patent to be obtained, but provides substantial costreductions.

THE DRAWINGS

FIG. 1 is a fragmentary view, partly in side elevation and partly insection, illustrating ignitor apparatus constructed in accordance withthe invention and mounted on a support forming part of an oven wall;

FIG. 2 is an exploded view of apparatus shown in FIG. 1, but omittingthe oven wall and the mounting means for the ignitor apparatus;

FIG. 3 is an elevational view of one end of the ignitor apparatus;

FIG. 4 is a greatly enlarged, fragmentary detail of that portion of FIG.3 within the dotted line circle; and

FIG. 5 is a greatly enlarged view illustrating the details of theignitor apparatus mounting means and the range of movement of theignitor apparatus.

DESCRIPTION OF THE DISCLOSED EMBODIMENT

Ignitor apparatus constructed in accordance with the disclosedembodiment of the invention is designated generally by the referencecharacter 1 and is adapted for installation in a commercial baking ovenof the kind having a combustion chamber or enclosure formed by walls,one of which is shown at 2 in FIG. 5. Although not shown in the drawingsthe oven includes within the enclosure one or more conveyors whichsupport and transport products longitudinally of the oven from an oveninlet to an oven outlet. The oven enclosure may include one or morelongitudinally spaced sections each of which has apparatus (not shown)for controlling temperature. At longitudinally spaced intervals each ofthe oven sections has laterally extending combustible fuel burners, oneof which is shown at 3 in FIGS. 3-5, and each such burner extendstransversely of the path along which the bakery products are moved bythe conveyors, as is conventional. Each burner 3 includes a hollow tube4 which partially occupies an opening 5 in the oven wall 2 and issupported by a support member 6 that is secured to the oven wall 2 bysuitable means such as bolts 7. The burner tube 4 has a fitting 8 at oneend thereof and external of the oven for connection to a supply ofcombustible fuel such as natural or propane gas. At one side of the tube4 is a ribbon fuel outlet 9 (FIGS. 3 and 4) through which the fuel gasmay pass into the interior of the oven. Depending on the size of theoven, the burner tube may be eight or more feet in length.

The ignitor apparatus 1 comprises an electrically conductive sleeve 10having plugs 11 and 12 at opposite ends thereof. Each plug is formed ofknown electrically insulating material which is capable of withstandingwithout adverse consequences the heat within the oven. Each plug has anaxial bore 13 through which extends an electrically conductive ignitorelectrode 14. The electrode 14 is bent at one end as at 15 to form anextension 16 which extends obliquely and terminates in a terminal 17which parallels the electrode 14.

That portion of the electrode 14 which spans the plugs 11 and 12 isencircled by an electrically non-conductive tube 18 formed of suitablematerial, such as Teflon.

Pinned or otherwise suitably fixed to the electrode 14 adjacent the plug12 is a transversely extending, restraining pin 19 that is accommodatedin a recess or slot 20 formed in the outer surface of the plug 12. Theopposite end of the electrode 14 is threaded as at 21 for theaccommodation of a nut 22. The threaded end of the electrode isencircled by a spring 23 which bears against the outer surface of theplug 11 and the confronting surface of the nut 22 so as constantly toexert a yieldable force on the electrode to maintain the restraining pin19 in the slot 20. At the free end of the threaded end of the electrodeis a fitting 24 which electrically connects the electrode to wiringforming part of an ignition circuit and an ignition sensor proving unit(ISPU) of the kind disclosed in the aformentioned U.S. Pat. No.6,808,389.

Welded to the outer surface of the sleeve 10 as at 25 is an electricallyconductive ground rod 26 to the free end of which is fixed anelectrically conductive, flag-like fuel gas concentrator 27. Theconcentrator 27 includes an electrically conductive, flag-like plate 28having a free end 29 which is bent so as to occupy a position spacedfrom the free end 17 of the electrode 14 by a gap 30 of predeterminedwidth. The width of the gap is such as to enable sparks to jump from theelectrode free end 17 to the free end 29 of the plate 28. To enhance theability of sparks to traverse the gap 30 the free end 17 of theelectrode is knurled as shown at 31 and the free end of the accumulatorplate 28 is provided with a sharp edge 32. See FIG. 4.

As is best shown in FIG. 5, the ignitor apparatus 1 is mounted on theoven wall 2 adjacent a burner tube 4 so that when installed the sleeve10 extends through an oversized opening 33 in the mounting plate 6 whichis adjacent the opening through which the burner tube 4 extends. Securedto the mounting plate 6 and externally of the oven is a mounting ring34. A bushing 35 has an annular body 36 having an annular projection 37which extends through the mounting ring 34 and is secured thereto by aset screw 38. The bushing 35 has an axial bore which extends in oppositedirections from a central point 39 and forms two annular passages 40 and41, both of which taper inwardly from opposite ends toward the centralpoint 39.

The bushing body 36 has a pair of opposed pivot and securing screws 46,each of which has a head at one end and a pointed free or opposite endwhich bears upon the sleeve 10. The head of each screw is accommodatedin a counterbore 44. The head of each screw seats on the base of itsrespective counterbore which is so located as to preclude movement ofthe screws inwardly a distance sufficient to pierce the wall of thesleeve 10. However, the pointed ends of the screws do slightly indentthe wall of the sleeve 10, thereby preventing movement of the sleevetransversely of the bushing and establishing a pivot axis about whichthe tube may rock from side to side as is indicated in dash lines inFIG. 5.

Following installation of the ignitor apparatus 1 on the oven wall thesleeve 10 is secured to the burner tube 4 by a bracket 46 (FIG. 3)having an arm 47 terminating at one end in a foot 48 which is fixed tothe adjacent burner tube 4. The opposite end of the arm 47 forms apartial loop 49 which partially encircles the ignitor sleeve 10. Theignitor apparatus 1, therefore, is secured at all times to the adjacentburner tube 4 so as to enable the ignitor apparatus to move with theburner tube in those instances in which it moves in response tovariations in ambient temperature within the oven.

It has been found that, in virtually all instances, the movement of aburner tube due to temperature variations is in a substantiallyhorizontal plane. Since the ignitor assembly sleeve 10 extends beyondthe opposite ends of the bushing 35, the tapers of the passages 40 and41 should be sufficient to enable the sleeve to partake of adequatemovement to avoid the imposition of bending stress on the sleeve 10 oron the support 6 when the sleeve moves. In the event the movement of theburner tube is not purely horizontal, the annular configuration of thepassages 40 and 41 through the bushing will enable the ignitor sleeve 10to move with the burner tube regardless of its direction of movement.

The heat of the oven may generate steam as a result of the baking ofproducts or from the heating of air within the sleeve 10. Accordingly,vent openings 50 are formed in that portion of the sleeve 10 which isexternal of the oven to enable air and/or steam to pass therethrough.Also external of the oven the ignitor sleeve 10 supports a terminal forelectrical circuitry 51 which completes the ignition and ground circuitto the ISPU apparatus (not shown) in the manner referred to in U.S. Pat.No. 6,808,389.

The disclosed ignitor apparatus is representative of a presentlypreferred embodiment of the invention, but is intended to beillustrative rather than definitive thereof. The invention is defined inthe claims.

1. In an oven assembly wherein combustible fuel is emitted from a burnertube within a combustion chamber, said burner tube being susceptible todistortion and movements in response to changes in ambient temperature,said fuel being ignitable by sparks generated by an ignition circuithaving ignitor and ground electrodes spaced from one another by a sparkgap and carried by a support member in such position as to locate saidgap in the path of fuel emitted from said burner tube, said supportmember being coupled to said burner tube for movements therewith, theimprovement comprising means mounting said support member in saidchamber for bodily rocking movements of said support member relative tosaid chamber in response to and in the directions of said movements ofsaid burner tube.
 2. The assembly according to claim 1 wherein saidmounting means comprises a bushing having a passage in which saidsupport member is accommodated, means for securing said bushing to saidchamber, and adjustable coupling means operable to maintain said supportmember in said bushing and enable pivotal movements of said supportmember relative to said bushing about an axis.
 3. The assembly accordingto claim 2 wherein said coupling means comprises at least one pin inengagement with said support member and preventing movement of saidsupport member transversely of said axis.
 4. The assembly according toclaim 3 wherein said pin defines said axis about which said supportmember is rockable.
 5. The assembly according to claim 2 wherein thepassage in said bushing is tapered inwardly from opposite ends of saidpassage.
 6. The assembly according to claim 2 wherein said axis issubstantially vertical.
 7. The assembly according to claim 1 includingat least one opening in said support member externally of said chamberand through which gas may pass into said support member.
 8. The assemblyaccording to claim 1 wherein at least one of said electrodes is knurledadjacent said gap.
 9. The assembly according to claim 1 wherein saidground electrode comprises a flag having a sharp edge confronting saidgap.
 10. An ignitor construction for use in igniting a combustible fuel,said construction comprising an elongate, tubular support member havingopposite ends and being formed of electrically conductive material;electrically conductive ignitor and ground electrodes electricallyinsulated from one another and carried by said support member in suchpositions relative to one another as to establish a gap across which anelectrically generated spark may jump; and swivel means mounting saidsupport member between the ends thereof for bodily rocking movements ofsaid support member about an axis.
 11. The construction according toclaim 10 wherein said swivel means comprises a bushing through whichsaid support member extends, and including pivot means reacting betweensaid bushing and said support member for enabling said rocking movementof the latter about said axis relative to said bushing.
 12. Theconstruction according to claim 11 wherein said bushing includes apassage therethrough, said passage flaring in opposite directions from apoint between opposite ends of said passage.
 13. The constructionaccording to claim 11 wherein said pivot means comprises a pair ofopposed pins carried by said bushing and extending toward one anotherfor engagement with said support member on opposite sides of the latter,and limit means for limiting movement of said pins in a direction towardsaid support member following engagement of said pins with said supportmember.
 14. The construction according to claim 10 wherein at least oneof said electrodes has a knurled surface adjacent said gap.
 15. Theconstruction according to claim 10 wherein one of said electrodescomprises a flag one end of which confronts the other of said electrodesand forms with the other of said electrodes the boundary of said gap.16. The construction according to claim 15 wherein said edge of said oneof said electrodes has a sharp surface confronting the other of saidelectrodes.
 17. The combination of an elongate burner tube susceptibleof distortion and movements in response to changes in ambienttemperature, said burner tube having an opening therein through whichcombustible fuel may flow along a path, and an ignitor for igniting fuelflowing through said opening, said ignitor comprising an elongatesupport member supporting a spark electrode and a ground electrodespaced from one another a distance to establish therebetween a sparkgap; means independent of said burner tube mounting said support memberin a position alongside but spaced a selected distance from said burnertube; and means coupling said support member to said burner tube formaintaining said support member in such position that said spark gaplies in the path of fuel flowing through said opening, said mountingmeans enabling said support member and the electrodes carried thereby toswivel in response to said movements of said burner tube and maintainsaid support member at said selected distance from said burner tube. 18.The combination according to claim 17 wherein said mounting meanscomprises a bushing having a passage in which said support member isaccommodated, and adjustable coupling means operable to maintain saidsupport member in said bushing and enable rockable movements of saidsupport member about an axis relative to said bushing.
 19. Thecombination according to claim 18 wherein said coupling means comprisesat least a pair of pins in engagement with said support member, saidpins defining said axis and preventing movement of said support membertransversely of said axis relative to said bushing.
 20. The combinationaccording to claim 18 wherein the opening in said bushing is taperedinwardly from opposite ends of said opening.